bug#26682: 26.0.50; Error at startup with minibuffer-only frame

[martin rudalics <rudalics@gmx.at>]

 > On Windows, however, even
 > with my patch, one out of ten times starting Emacs with Stefan's command
 > line hangs it with the initial frame visible and I have to quit with
 > C-g.
 >
 > More precisely, it hangs in ‘frame-notice-user-settings’ in the while
 > loop below
 >
 >          ;; MS-Windows needs this to avoid inflooping below.
 >          (if (eq system-type 'windows-nt)
 >          (sit-for 0 t))
 >          ;; If the frame isn't visible yet, wait till it is.
 >          ;; If the user has to position the window,
 >          ;; Emacs doesn't know its real position until
 >          ;; the frame is seen to be visible.
 >          (while (not (cdr (assq 'visibility
 >                     (frame-parameters frame-initial-frame))))
 >            (sleep-for 1))
 >
 > and it does so always when I run Emacs under GDB.  I don't yet know why
 > it hangs: The request to make the frame visible is posted orderly but
 > somehow SET_FRAME_VISIBLE gets never executed.  Can you reproduce it?

FYI it's caused by WM_MOVE which OT1H is likely counted by the

     for (count = input_signal_count + 10;
	 input_signal_count < count && !FRAME_VISIBLE_P (f);)

loop in x_make_frame_visible and OTOH lacks a SET_FRAME_VISIBLE (f, 1).

martin